The parafacial zone (PZ) in the brain stem produces half of all the brain’s sleep-promoting activity.

For the first time ever, neuroscientists have used an innovative new method to identify a circuit in the brain that promotes deep sleep, which reinvigorates the brain from its daily activities.

The ‘sleep-node’ — the second to be discovered — lies deep in the ancient part of the brain and is vital in sending us off into a ‘slow-wave’ or deep sleep, which is one of the stages of sleep we cycle through during the night.

The area is in the parafacial zone (PZ) in the brain stem, and it produces half of all the brain’s sleep-promoting activity.

Neuroscientists used a sophisticated new approach to turn this region of the brain on and off in mice.

Patrick Fuller, one of the study’s authors, explains:

“To get the precision required for these experiments, we introduced a virus into the PZ [parafacial zone] that expressed a ‘designer’ receptor on GABA neurons only but didn’t otherwise alter brain function.

When we turned on the GABA neurons in the PZ, the animals quickly fell into a deep sleep without the use of sedatives or sleep aids.”

How the parafacial zone in the brain stem interacts with other areas of the brain is not yet known, but this is an important new tool in investigating the function of different areas of the brain.

Christelle Ancelet, another of the study’s authors, said:

“These new molecular approaches allow unprecedented control over brain function at the cellular level.

Before these tools were developed, we often used ‘electrical stimulation’ to activate a region, but the problem is that doing so stimulates everything the electrode touches and even surrounding areas it didn’t.

It was a sledgehammer approach, when what we needed was a scalpel.”

Caroline E. Bass, another of the study’s authors, commented:

“We are at a truly transformative point in neuroscience, where the use of designer genes gives us unprecedented ability to control the brain.

We can now answer fundamental questions of brain function, which have traditionally been beyond our reach, including the ‘why’ of sleep, one of the more enduring mysteries in the neurosciences.”

The scientists hope the findings will eventually lead to new treatments for sleep disorders like insomnia.